Metal matrix composites (MMC) comprising a metal matrix and a reinforcing phase such as ceramic particulates, show great promise for a variety of applications because they combine the stiffness and wear resistance of the reinforcing phase with the ductility and toughness of the metal matrix.
Various metallurgical processes have been described for the fabrication of metal matrix composites. These methods are, for instance, based on powder metallurgy techniques and liquid metal infiltration techniques which make use of pressure casting, vacuum casting, stirring and wetting agents. Pressure Infiltration Casting as described in U.S. patent application Ser. No. 07/325,221 by Arnold J Cook and entitled "Method and Apparatus for Casting" described pressure casting apparatus whereby the mold, metal and heating means are contained within a pressure vessel. The described method for casting essentially comprises the steps of evacuating the pressure vessel while melting the metal within a crucible. The mold, comprising a preform, has a snorkel and is disposed on top of the crucible. The molten metal is fluidically connected to the mold by disposing the snorkel in the crucible of molten metal, thereby isolating the inside of the mold from the interior of the pressure vessel. Inert pressurized gas is then used to pressurize the vessel thereby forcing the molten metal into the mold. Since the mold is contained within a pressure vessel, the pressure acts on the outside of the mold and the inside of the mold. By controlling the rate of pressurization, the forces on the inside and the outside of the mold can be essentially balanced such that a thin walled mold can be used.
Previous methods of forming metal matrix components have been slow and tedious. The present invention describes an apparatus which decreases the time of production runs by using a novel combination of elements including separate melt and mold chambers and separable mold halves to eject the metal matrix component from within.